Overview
EN ISO 16634-2:2016 (ISO 16634-2:2016) specifies a standardized laboratory method for determining total nitrogen by combustion (the Dumas principle) and for calculating crude protein content of cereals, pulses and milled cereal products. Endorsed by CEN, this part of ISO 16634 provides procedural requirements, calibration guidance and reporting rules for reliable protein determination used in food analysis and quality control.
Key Topics and Technical Requirements
- Principle: Combustion (Dumas) converts nitrogen in a sample to simple gases which are measured to obtain total nitrogen. Results are converted to crude protein using established conversion factors.
- Scope limitation: Applies specifically to cereals, pulses and milled cereal products; it does not distinguish protein nitrogen from non‑protein nitrogen (similar limitation to the Kjeldahl method).
- Apparatus & reagents: Requirements for Dumas-type analyzers, oxygen control and reagents are specified to ensure accuracy and safety.
- Sampling & sample preparation: Procedures for representative sampling and homogenization of cereals and milled products are included.
- Procedure & calibration: Test portion selection, control of oxygen supply, instrument calibration, detection and data processing steps are defined to ensure traceable results.
- Calculation & expression of results: Formulas for nitrogen content and conversion to crude protein content are provided; different conversion factors may be applied depending on product type.
- Precision and uncertainty: Repeatability, reproducibility and interlaboratory precision data, plus guidance on uncertainty and critical differences for result comparison.
- Reporting: Required elements of the test report (method reference, sample identification, results, calibration status and uncertainty) are defined.
Applications and Who Uses It
- Food and cereal laboratories performing protein analysis for nutritional labeling and quality control.
- Cereal and pulse processors and millers verifying raw material and product specifications.
- Regulatory bodies and inspection labs enforcing food standards and trade specifications.
- Research institutions studying composition, breeding or processing effects on protein content.
- Third‑party testing laboratories offering accredited analytical services (ISO/IEC 17025).
Practical benefits of the Dumas method highlighted in the standard include faster analysis, automation potential and avoidance of hazardous reagents used in Kjeldahl testing. Note: Dumas measurements may yield slightly higher nitrogen values than Kjeldahl due to broader detection of non‑protein nitrogen.
Related Standards
- EN ISO 16634-1 / ISO 16634-1 (Part 1: oilseeds and animal feeding stuffs)
- ISO 712 (moisture determination for cereals) - referenced for sample moisture considerations
- Kjeldahl method standards (for comparative context)
Keywords: EN ISO 16634-2:2016, Dumas method, total nitrogen, crude protein content, cereals, pulses, milled cereal products, protein determination, food analysis, laboratory calibration.